256 University of California Publicatio)is i)i Zoology. [Vol. 7 



sprinkling of hairs which are black rather than dark brown. 

 Intermedins may be said to be grayish, whik^ ciirlatus is light 

 brownish. Face of iutcrmedius gray; that of ciirtahts brown. 

 No. 28341 has begun to assume the post-breeding pelage, the molt 

 proceeding medially, and having appeared as yet only on the 

 head. In general the two species are similar in coloration, but 

 intermedius is definitely smaller, especially in cranial measure- 

 ments, in which the difference in size is relatively great. The 

 auditory bullae are smaller, relatively and actually, the rostrum 

 'and incisors are narrower, the jugal is not so wide; the anterior 

 expansion of the zygomatic arch is not as extensive, and the in- 

 fraorbital foramen is smaller. Although in general the two skulls 

 are nuicli alike in shape, skulls of intermedius are not so definitely 

 concave post-orbitally ; notch enclosed by the hamular or coronoid 

 of the mandible not so rounded as in curt at us but more as in 

 paUidus; neck of articular process of mandible not so constricted; 

 angular process slightly more scooped out internallj^ 



Microtus intermedius is so different from pallidus as hardly 

 to necessitate comparison. A specimen of the latter (no. 110803, 

 female, GlenuUin, North Dakota, Sept. 12, 1901, W. H. Osgood) 

 is at hand. It is assuming the winter pelage, which covers the 

 face and top of the head and is gradually encroaching on the 

 back along the median line. The new pelage is much darker than 

 that which is being replaced. Intermedius is readily distin- 

 guished from pallid us by a lack of huffy on the ears and nose, 

 which is a conspicuous feature in that form. Pallidus, at least 

 as exemplified by the specimen at hand, instead of being the 

 palest of the species of Microtus of the subgenus Lagurus (see 

 Bailey, 1900, p. 68) is exceeded in this respect by both the avail- 

 able specimen of curtatus (no. 28341) and all our specimens of 

 the new species. At the present state of knowledge, the distinc- 

 tion of being in general the palest of the species must be accorded 

 intermedius. The new form is smaller than pallidus except in 

 the matter of tail length. The skull is also perceptibly smaller, 

 having rostrum iiion; narrow, though the auditory bullae are 

 slightly larger. 



DisTKiBi'TiON. — Although cxlcnsive ti-ai)])ing was carried on 

 at several point.s in the Ti-ansition zone of the Pine Foi-est 



